Biodegradable magnesium alloy

ABSTRACT

A magnesium alloy includes a rare earth element alloy component comprising yttrium, a rare earth element (REE) other than yttrium, and a balance of magnesium. The rare earth element other than yttrium may comprise two or more rare earth elements other than yttrium. The rare earth element other than yttrium may include a heavy rare earth element and a light rare earth element. The alloy may include about 4-10 wt-% yttrium, 0-9 wt-% heavy REE, 0-7 wt-% light REE, 0-7 wt-% zinc, 0-0.7 wt-% zirconium, and a balance of magnesium. The balance of magnesium may be in an amount up to 90 wt-%.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/108,923, filed Jan. 28, 2015, which is incorporated herein by reference for all purposes.

BACKGROUND

Magnesium demonstrates specific properties that may be suitable in several mobile and medical applications. For example, in various medical applications, such as cardiovascular or orthopedic, magnesium may be biodegradable, or bioabsorbable, and less toxic than other conventional materials.

The use of magnesium in many applications is inhibited by potentially high degradation rates and related losses in mechanical integrity. Furthermore, the impurities typically found in magnesium, such as nickel, copper, and iron, may compound the problem by enhancing the corrosion rate.

The discussion of prior publications and other prior knowledge does not constitute an admission that such material was published, known, or part of the common general knowledge.

SUMMARY

It is desirable to develop a suitable magnesium alloy that is lightweight compared to conventional materials used in a broad range of applications (e.g., mobile or medical) that exhibits significantly improved properties (e.g., per unit mass or volume). Non-limiting examples of improved properties include bioabsorbability/biodegradability, biocompatibility (e.g., low toxicity), creep resistance, corrosion resistance, strength, toughness, durability, flexibility, deliverability, minimal recoil, ductility, elongation to failure, castability, and grain refinement, which may be defined at various application-specific temperatures (e.g., room temperature, body temperature, etc). In particular, improved mechanical and corrosion performance over existing magnesium and magnesium alloys may be provided.

In one illustrative embodiment, an alloy comprises a rare earth element alloy component in an amount greater than 6 wt-% and magnesium in an amount up to about 90 wt-%. The rare earth element alloy component comprises yttrium in an amount greater than 2 wt-% and a rare earth element other than yttrium in an amount greater than 1 wt-%. The rare earth element other than yttrium may be selected from gadolinium, dysprosium, erbium, neodymium, lanthanum, cerium, and combinations thereof.

In another illustrative embodiment, an alloy comprises a rare earth element alloy component and magnesium in an amount up to about 90 wt-%. The rare earth element alloy component comprises yttrium in an amount greater than 3 wt-% and a rare earth element other than yttrium in an amount greater than 1%. The rare earth element other than yttrium may be selected from gadolinium, dysprosium, erbium, neodymium, lanthanum, cerium, and combinations thereof.

In a further illustrative embodiment, an alloy comprises a rare earth element alloy component and magnesium in an amount up to about 90 wt-%. The rare earth element alloy component comprises yttrium in an amount greater than 3 wt-% and a heavy rare earth element other than yttrium in an amount no less than 0.1 wt-%. The heavy rare earth element may be selected from gadolinium, dysprosium, erbium, and combinations thereof.

In yet another illustrative embodiment, an alloy comprises a rare earth element alloy component in an amount no less than 10 wt-% and magnesium. The rare earth element alloy component comprises yttrium in an amount greater than 2 wt-% and a rare earth element other than yttrium in an amount greater than 1 wt-%. The rare earth element other than yttrium may be selected from gadolinium, dysprosium, erbium, neodymium, lanthanum, cerium, and combinations thereof.

In some embodiments, the amount of yttrium may be no less than 4.5 wt-%. In at least one embodiment, the amount of rare earth element other than yttrium may be no less than 4 wt-%. The amount of the rare earth element alloy component may be no less than 9.5 wt-%. The rare earth element other than yttrium may be a heavy rare earth element selected from gadolinium, dysprosium, and erbium.

In further embodiments, the amount of the rare earth element other than yttrium is no less than 5 wt-%. The rare earth element other than yttrium may comprise a combination of two rare earth elements other than yttrium. The rare earth element other than yttrium may comprise a heavy rare earth element and a light rare earth element. The heavy rare earth element may be selected from gadolinium, dysprosium, erbium and combinations thereof. The light rare earth element may be selected from selected from neodymium, lanthanum, cerium, and combinations thereof.

In at least one embodiment, the amount of the heavy rare earth element is greater than the amount of the light rare earth element. In at least one other embodiment, the amount of yttrium is greater than or equal to the amount of the rare earth element other than yttrium.

In various further embodiments, the alloy comprises at least one of zinc in an amount greater than 0.1 wt-% and zirconium in an amount greater than 0.3 wt-%.

In various additional embodiments, the alloy comprises a substantial absence of an element selected from scandium in an amount less than 1 wt-%, calcium in an amount less than 0.05 wt-%, indium in an amount less than 0.1 wt-%, and combinations thereof.

The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The detailed description that follows more particularly exemplifies illustrative embodiments. In several places throughout the application, guidance is provided through lists of examples and illustrative embodiments, which may be used in various combinations. In each instance, the recited list serves only as a representative group and should not be interpreted as an exclusive list. Various other features and advantages will become apparent upon reading the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of the following detailed description of various embodiments of the disclosure in connection with the accompanying drawings.

FIGS. 1A, 1B, and 1C are each visualizations of imaging data at various scales for a magnesium alloy of the present disclosure. FIG. 1A shows a visualization of scanning electron microscope (SEM) data at a 100 micron scale (e.g., micrometers). FIG. 1B shows a visualization of the SEM data of FIG. 1A at a 10 micron scale. FIG. 1C shows a visualization of the SEM data of FIG. 1A at a 2 micron scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In the following detailed description, reference is made to several specific embodiments. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense.

All scientific and technical terms used herein have meanings commonly used in the art unless otherwise specified. The definitions provided herein are to facilitate understanding of certain terms used frequently herein and are not meant to limit the scope of the present disclosure.

Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein.

The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range. Herein, the terms “up to” or “no greater than” a number (e.g., up to 50) includes the number (e.g., 50), and the term “no less than” a number (e.g., no less than 5) includes the number (e.g., 5).

Unless otherwise noted, all parts, percentages, ratios, etc. are by weight. Weight percent is defined by the percentage of a component in the composition of components (e.g., 10 wt-% of an alloy component means that 10 percent of the weight of the alloy is the alloy component). The weight may be measured by any suitable technique, such as energy dispersive x-ray spectroscopy (EDS) or inductively coupled mass spectrometry (ICP-MS), for example. References to “about” X wt-% may refer to the precision of the instrument for measuring weight or the precision of available components for manufacturing, for example. These abbreviations are used herein: wt=weight, atm=atomic, ° C.=degrees Celsius, and ppm=parts per million.

As used herein, “have”, “having”, “include”, “including”, “comprise”, “comprising” or the like are used in their open ended sense, and generally mean “including, but not limited to”. It will be understood that “consisting essentially of”, “consisting of”, and the like are subsumed in “comprising,” and the like.

As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” encompass embodiments having plural referents, unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

Also used herein, a “balance” is used to indicate at least part of the remaining portion of a composition or the entire remaining portion. For example, a composition comprising 10 wt-% alloy component and a balance of magnesium means that at least part or the entire remaining portion of the composition (e.g., up to 90 wt-%) is magnesium. The balance of material may include impurities in the balance material utilized in the composition (e.g., 99.99 wt-% pure magnesium comprises 0.01 wt-% impurity in the magnesium). Further, the balance of material may include other material in an amount generally less than the amount (e.g., wt-%) of the balance material utilized in the composition (e.g., a balance of magnesium up to 90 wt-% does not exclude 1 wt-% zirconium, 6 wt-% zinc, etc.).

The term “and/or” means one or all of the listed elements or a combination of any two or more of the listed elements (e.g., casting and/or treating an alloy means casting, treating, or both casting and treating the alloy).

The phrases “at least one of,” “comprises at least one of,” and “one or more of” followed by a list refers to any one of the items in the list and any combination of two or more items in the list.

Reference to “one embodiment,” “an embodiment,” “certain embodiments,” or “some embodiments,” etc., means that a particular feature, configuration, composition, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of such phrases in various places throughout are not necessarily referring to the same embodiment of the disclosure. Furthermore, the particular features, configurations, compositions, or characteristics may be combined in any suitable manner in one or more embodiments.

The words “preferred,” “preferably,” and “optionally” refer to embodiments of the disclosure that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the disclosure.

The present disclosure provides a magnesium and rare earth element alloy. In particular, the magnesium alloy includes yttrium and at least one other rare earth element. The alloy may be lightweight and may exhibit significantly improved properties (e.g., per unit mass or volume). Non-limiting examples of improved properties include bioabsorbability/biodegradability, biocompatibility (e.g., low toxicity), creep resistance, corrosion resistance, strength, toughness, durability, flexibility, deliverability, minimal recoil, ductility, elongation to failure, castability, and grain refinement, which may be defined at various application-specific temperatures (e.g., room temperature, body temperature, etc).

The alloy may be used in a broad range of applications, which may be mobile or medical, for example. Non-limiting examples of medical applications include bioabsorbable/biodegradable heart stents, valve scaffolds, staples, bone screws, and fasteners. Non-limiting examples of mobile applications include bicycle components (e.g., frame), aircraft components, automobile components, and electronics enclosures or components (e.g., laptop).

Desirable properties may have different priorities for different applications. In a medical stent application (e.g., cardiovascular stent), for example, corrosion performance of the alloy may be more important than ductility or strength, and ductility may be more important than strength. In a medical fixation application (e.g., staples, orthopedic screws, fasteners, etc), for example, ductility of the alloy may be more important than strength or corrosion performance, and strength may be more important than corrosion performance. The balance of elements in the alloy may be selected to achieve the desired priority of properties as described herein in more detail.

In general, the alloy includes magnesium and one or more alloying components. The alloy may include one alloying component. The alloy may include two alloying components. The alloy may also include three, four, five, six, or seven alloy components, among others. In many embodiments, each alloy component may be introduced to modify or improve the properties of magnesium, for example, by way of solid solution strengthening, precipitation hardening, grain-boundary strengthening, or combinations thereof.

In illustrative embodiments, the alloy includes a solid solution alloy component. The atoms of the solid solution alloy component (e.g., rare earth element or metal) can diffuse into the crystalline lattice (e.g., matrix) of a base metal (e.g., magnesium) to substitute for base metal atoms or to fill the interstices in the base metal matrix. Magnesium has a hexagonal close-packed (hcp) crystal structure with an ideal axial ratio (c/a) of 1.624 and an atomic diameter of 0.320 nanometers (nm) and may form solid solutions with a diverse range of elements, such as rare earth elements and metals, which may be selected to strengthen the magnesium matrix, for example.

In various embodiments, the alloy includes a grain refiner. The grain refiner (e.g., zirconium) can be introduced to a magnesium alloy melt to limit the growth of grains as the melt is cooled below a melting temperature (e.g., casting temperature). The limited size of the grain increases the presence of grain boundaries, which may limit the propagation of dislocations (e.g., defects in the crystalline lattice) in the matrix and may improve strength of the alloy.

In many embodiments, the alloy includes one or more precipitates (e.g., impurity phase). In at least some embodiments, the alloy component has a high temperature-dependent solubility in magnesium. Precipitate particles may be formed due to changes in solid solubility (e.g., rare earth element or metal solubility in magnesium) with temperature, which may produce particles of an impurity phase that may limit the propagation of dislocations in the matrix. A heat treatment may be used to form or grow the precipitate particles at an annealing temperature below a melting temperature (e.g., casting temperature) and in a heat treatment window.

In one case, a cast alloy is formed using a conventional casting technique. The magnesium and alloying components are heated together in a crucible to a suitable casting temperature to form a liquid alloy, or melt, and the liquid alloy is poured into a static mold and allowed to cool to the room temperature (e.g., 25° C.). The formed alloy may be utilized as a whole or be separated into multiple pieces of alloy (e.g., ingots).

In another case, a cast alloy is formed using a continuous casting technique. The melted, liquid alloy is continuously poured into a mold that forms a strand of alloy instead of a static mold. The strand moves through the mold and is continuously cooled by quenching with water along the whole of the strand, which may form a thin solidified shell on the cast. The strand may be cut, for example, by a torch, to form separate pieces of alloy (e.g., ingots).

The microstructure of a continuously cast alloy may be slightly different than that of an alloy formed in conventional casting. For example, the grain structure may be more refined, and the chemical composition and microstructure may be more uniform across the thickness of the cast.

In yet another case, a cast alloy is formed using a rapid solidification process. For example, the melted, liquid alloy may be poured onto a fast-rotating copper wheel. The wheel may freeze the alloy instantaneously, in some cases, via cooling at a rate of 1,000,000° C. per second. A homogenous crystalline structure of the alloy may be retained in the material. The rotation of the wheel may further direct the alloy toward a chopper to form separate pieces of alloy (e.g., ingots).

Magnesium (Mg) utilized in the alloy may be have various levels of purity. In various embodiments, magnesium is provided in ultra-pure form (e.g., 99.999 wt-% magnesium or less than 10 ppm non-Mg components). Ultra-pure magnesium may have a creep resistance that does not exceed about 0.02 mg/cm²/day in many cases. However, ultra-pure magnesium is typically manufactured by the expensive process of vacuum sublimation to achieve the high purity level and creep resistance, which impedes its use in many applications, at least due to cost-effective availability.

In many embodiments, magnesium utilized in the alloy may be in non-ultra-pure form. In other words, the magnesium in the alloy may have a purity level no greater than about 99.999 wt-% magnesium (e.g., no less than 10 ppm non-Mg components) and/or a creep resistance greater than about 0.02 mg/cm²/day. The use of non-ultra-pure magnesium may be preferable in applications wherein availability and cost-effective manufacturing are more important, such as certain medical applications, as well as many mobile applications.

In illustrative embodiments of the alloy, one or more alloy components and magnesium are included. Generally, the magnesium is present in a greater amount than another element or all other elements, including alloying components. Thus, the alloy may conveniently be described as a magnesium alloy (e.g., primarily comprising magnesium). In some particular embodiments, the alloy includes magnesium in an amount up to 90 wt-% (e.g., alloy components are present in an amount of at least 10 wt-%). In at least one embodiment, the alloy includes magnesium in an amount up to 89.5 wt-%. In some illustrative embodiments, the alloy includes various alloy components and a balance of magnesium (e.g., the balance of material in the alloy).

The alloy may include various alloying components. In particular, the alloy may include a rare earth element (REE) alloy component, which may comprise one or more specific rare earth elements. Specific rare earth elements include scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

In general, the rare earth element alloy component includes yttrium. In many embodiments, the rare earth element alloy component includes yttrium and a rare earth element other than yttrium. In some embodiments, the rare earth element alloy component includes yttrium and two rare earth elements other than yttrium. As used in the description herein, “rare earth element” may mean “rare earth element other than yttrium,” as will be made clear by the context of usage.

In addition, the term “rare earth element” may refer to a subset of known rare earth elements. The REEs referred to may be only those commercially available. In particular, the REEs may refer to those commercially available in a pure form. A pure form may include 99 wt-% REE, 99.9 wt-% REE, or 99.99 wt-% REE, among others. For example, a rare earth element added to the alloy may optionally be provided in 99.99 wt-% REE form. In other embodiments, the rare earth element can be provided as misch-metal (e.g., an alloy of various rare earth elements, which may include cerium, lanthanum, neodymium, and praseodymium). Although the rare earth element can be provided in any form, in illustrative embodiments, only pure rare earth elements are used to form the alloy.

In certain illustrative embodiments, the term “rare earth element” in the alloy may refer to the subset of rare earth elements (e.g., other than yttrium) selected from gadolinium, dysprosium, erbium, neodymium, lanthanum, cerium, and combinations thereof. In various embodiments, a rare earth element other than yttrium is selected from gadolinium, dysprosium, erbium, neodymium, and combinations thereof. In at least some embodiments, a rare earth element other than yttrium is selected from gadolinium, neodymium, or both.

Furthermore, rare earth elements may be classified herein, for example, into light rare earth elements (light REEs) and heavy rare earth elements (heavy REEs), which corresponds to relative atomic number or weight. In various embodiments, a rare earth alloy element other than yttrium is selected from a light REE, a heavy REE, or both.

For example, in some embodiments, a light REE is selected from lanthanum, cerium, praseodymium, neodymium, promethium, and combinations thereof. In further embodiments, a light REE is selected from neodymium, lanthanum, cerium, and combinations thereof. In yet further embodiments, a light REE is neodymium.

Also, for example, in various embodiments, a heavy REE is selected from samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and combinations thereof. In further embodiments, a heavy REE is selected from gadolinium, dysprosium, erbium, and combinations thereof. In yet further embodiments, a heavy REE is gadolinium.

One or more alloying components may be provided in an amount that is at least partially soluble in magnesium, at least partially insoluble in magnesium, or both depending on temperature. The solubility may refer to liquid solubility, solid solubility, or both, for example. In general, solubility in magnesium versus temperature mainly depends on the atomic size of the alloy component with regard to magnesium and its valence band configuration. In some specific examples, at about room temperature (e.g., 25° C.), neodymium has a solid solubility limit of less than about 1 wt-% in magnesium, gadolinium has a solubility limit of about 4 wt-% in magnesium, zinc has a solubility limit of about 2 wt-%, zirconium is not soluble, and yttrium is not soluble.

In many embodiments, one or more alloying components are included in the alloy below the solubility limit of magnesium at a desired temperature (e.g., the application requires use at room temperature or body temperature). In some embodiments, one or more alloying components are included in the alloy above one-fourth, one-third, one-half, etc. the respective solid solubility in magnesium. In various embodiments, one or more alloying components are included in the alloy above the respective solubility in magnesium, which may result in precipitates at room temperature, for example. In particular illustrative embodiments, an alloy component (e.g., yttrium, another rare earth element, or both) are included above their respective solubility limits in magnesium. The present disclosure recognizes that the inclusion of more than one alloying component in the alloy may alter the solubility of each respective alloying component (e.g., element) in magnesium.

Although the soluble amount of an alloy component may strengthen the matrix or have other desirable effects on the properties of magnesium alloy, the insoluble amount of an alloy component may form precipitate particles at various temperatures and provide further desirable effects on the magnesium alloy. Precipitate particles at a desired temperature may be useful in certain applications (e.g., for grain refinement and/or precipitate hardening).

A precipitate particle may be of a particular type, or phase, and the amount of each alloy component, relative amounts of each alloy component, or total of the alloy components may determine the precipitate phases formed in the alloy at the desired temperature. For example, the amount of yttrium, rare earth element, and/or any other alloy component may be selected to form precipitates with magnesium or another alloying component, which may improve the mechanical properties of the magnesium alloy. In some illustrative embodiments, the alloy includes magnesium-rich precipitates. In various illustrative embodiments the amount of yttrium is selected to form yttrium-rich precipitates, the amount of rare earth element is selected to form REE-rich precipitates, the amount of another particular alloy element is selected to form a particular alloy element-rich precipitate, or combinations thereof. The precipitates may be visible by imaging, such as computed tomography (CT), scanning electron microscopy (SEM), etc., which may facilitate identification and analysis of the precipitate phases and particles.

The one or more alloying components may be selected for their desirable effects on the properties of the magnesium alloy. In one example, the amount of yttrium may be selected to improve mechanical properties, such as elongation to failure and/or strength of the alloy. Yttrium may improve creep resistance in a range of temperatures. In various medical applications, for example, creep resistance at body temperature is important to maintaining the shape of a component comprising the alloy, such as in a cardiovascular stent application.

To illustrate potential amounts of yttrium, in many embodiments, the alloy can include yttrium in an amount greater than about 1 wt-%, greater than about 2 wt-%, greater than about 3 wt-%, no less than about 4 wt-%, no less than about 4.5 wt-%, no less than about 5 wt-%, greater than about 5.5 wt-%, no less than about 5.7 wt-%, no less than about 6 wt-%, no less than about 6.7 wt-%.

Furthermore, in various embodiments, the alloy includes yttrium in an amount up to about 10 wt-%, up to about 9 wt-%, up to about 7.7 wt-%, up to about 7 wt-%, up to about 6.7 wt-%, up to about 6 wt-%, or up to about 5 wt-%.

Yet further, in some embodiments, the alloy includes yttrium in an amount ranging from about 4.5 to about 7.7 wt-%, from about 5 to about 7 wt-%, from about 5.5 to about 6.7 wt-%, from about 5.7 to about 10 wt-%, from about 6 to about 10 wt-%, from about 6.7 to about 9 wt-%, or from about 4 to about 6 wt-%.

In at least one embodiment, the alloy includes yttrium in an amount equal to about 5 wt-%. The ranges or specific amount of yttrium may be selected depending on the particular application, some of which are described herein.

Other than yttrium, a rare earth element may also be included in the alloy to augment the same or additional properties of the magnesium alloy. For example, the rare earth element may be selected to improve corrosion resistance and/or mechanical properties of the alloy. The rare earth element other than yttrium may improve the strength of the alloy at elevated temperatures and/or may reduce porosity in casting (e.g., by reducing the freezing range).

To illustrate potential amounts of yttrium, in many embodiments, the alloy includes a rare earth element other than yttrium in an amount greater than 0 wt-%, no less than about 0.1 wt-%, greater than about 1 wt-%, greater than about 3 wt-%, no less than about 4 wt-%, no less than about 4.5 wt-%, no less than about 5 wt-%, greater than about 5.5 wt-%, or no less than about 6 wt-%.

Further, in various embodiments, the alloy includes a rare earth element other than yttrium in an amount no greater than about 9 wt-%, no greater than about 8 wt-%, no greater than about 7 wt-%, no greater than about 6 wt-%, no greater than about 5.5 wt-%, no greater than about 5 wt-%, no greater than about 4 wt-%, no greater than about 3.5 wt-%, no greater than about 3 wt-%, less than about 2.5 wt-%, no greater than about 2 wt-%, or no greater than about 1 wt-%.

Yet further, in some embodiments, the alloy includes a rare earth element other than yttrium in an amount ranging from about 0 to about 4 wt-%, from about 0 to about 3 wt-%, from about 0 to about 2 wt-%, from about 4 to about 6 wt-%, from about 5 to about 7 wt-%, from about 4.5 to about 9 wt %, or from about 5.5 to about 9 wt-%.

In further embodiments, the alloy includes a rare earth element other than yttrium in an amount equal to about 1 wt-%, about 5 wt-%, or about 6 wt-%. The ranges or specific amount of rare earth element may be selected depending on the particular application, some of which are described herein.

In illustrative embodiments, the rare earth element may include at least one heavy REE, at least one light REE, or both. For example, in some illustrative embodiments, the rare earth element other than yttrium is a heavy REE. In at least one embodiment, the rare earth element other than yttrium is gadolinium. Gadolinium may useful as it has the highest solubility in magnesium as compared to other rare earth element or heavy REE candidates. Yet in various illustrative embodiments, the rare earth element other than yttrium is a light REE. In at least one embodiment, the rare earth element other than yttrium is neodymium. Neodymium may be useful, in part, due to its cost-effective availability as a rare earth element.

The amount of rare earth element in the alloy may be set relative to the amount of yttrium. For example, the relative amount of each element may influence the properties of the alloy. The rare earth element may be included in an amount greater than, no greater than, less than, no less than, or about equal to the amount of yttrium.

In various illustrative embodiments, the rare earth element comprises only one specific rare earth element. However, in other illustrative embodiments, the rare earth element comprises a combination of specific rare earth elements. For example the rare earth element other than yttrium may comprise two or more rare earth elements, such as a first REE, a second REE, etc. In at least one embodiment, the rare earth element other than yttrium comprises two rare earth elements other than yttrium.

There may be advantages in including at least two rare earth elements in the alloy. For example, a second REE may be selected as a substitute for a first REE and may impart similar improvements in alloy properties. In some cases, the second REE may be selected as a more cost-effective substitute for the first REE. Each specific rare earth element (e.g., first REE, second REE, etc) may be included in any amount as described herein for the rare earth element, for example.

In addition to the various ranges and specific amounts described herein for each alloy component, the alloy may include two or more alloy components in a particular range or specific amount as a total amount, which may be selected to achieve certain desirable properties (e.g., more than one type/phase of precipitate). For example, in many embodiments, the rare earth element alloy component includes yttrium and the rare earth element other than yttrium (including potential combinations) in a total amount greater than about 6 wt-%, no less than about 6.5 wt-%, no less than about 9.5 wt-%, no less than about 10 wt-%, or no less than about 10.5 wt-%. In various embodiments, the REE alloy component includes yttrium and one or more rare earth elements in a total amount no greater than about 15.7 wt-%. The REE alloy component may include yttrium and a first REE. The REE alloy component may also include yttrium, a first REE, and a second REE.

In various embodiments, the rare earth element comprises a combination of two or more rare earth elements other than yttrium in a total amount greater than about 4 wt-%, greater than about 5 wt-%, no less than about 5.5 wt-%, or no less than about 6 wt-%.

In some embodiments, a first REE may be a heavy REE and a second REE may be a light REE. For example, the heavy REE may be gadolinium. The light REE may be neodymium. In at least one embodiment, the rare earth element includes gadolinium and neodymium.

In additional embodiments, the alloy may also optionally include an alloy component other than a rare earth element. For example, the alloy may include a metal as an alloy component. In some cases, the alloy may include zinc, zirconium, or both. In some conventional alloys, aluminum is used for castability. Instead, in many embodiments, zinc may be included in an amount to improve castability. Zirconium may be included in an amount for grain refinement and/or improvement of mechanical properties.

In many embodiments, the alloy includes zinc in an amount greater than 0 wt-%, no less than about 0.1 wt-%, no less than about 0.2 wt-%, or no less than about 0.22 wt-%. In various embodiments, the alloy includes zinc in an amount no greater than about 7 wt-%, no greater than about 6 wt-%, no greater than about 0.3 wt-%, or no greater than about 0.2 wt-%. In at least one embodiment, the alloy includes zinc in an amount of about 0.2 wt-%.

In many embodiments, the alloy includes zirconium in an amount greater than 0 wt-%, no less than about 0.3 wt-%, no less than about 0.4 wt-%, no less than about 0.5 wt-%, or no less than about 0.6 wt-%. In various embodiments, the alloy includes zirconium in an amount no greater than about 0.7 wt-%, no greater than about 0.6 wt-%, no greater than about 0.5 wt-%, or no greater than about 0.4 wt-%. In at least one embodiment, the alloy includes zirconium in an amount of about 0.4 wt-%. In at least one other embodiment, the alloy includes zirconium in an amount of about 0.6 wt-%.

In addition to including certain elements in the alloy, other elements may be substantially absent in the alloy, which may affect the properties of the alloy and/or the cost of manufacturing the alloy. In many embodiments, a substantial absence of an element comprises an amount of the element less than about 1 wt-%, less than about 0.1 wt-%, less than about 0.05 wt-%, less than about 0.01 wt %, less than about 0.001 wt-% (e.g., 10 parts per million), or about 0 wt-%. In some embodiments, elements substantially absent in the alloy are selected from aluminum, calcium, indium, manganese, scandium, silicon, zinc, or zirconium, as well as any selected rare earth element (e.g., a rare earth element other than yttrium, such as lutetium, a heavy REE, a light REE, etc), and combinations thereof.

Illustrative embodiments of particular alloys disclosed herein may be described as Mg—Y—Gd alloys, Mg—Y—Nd alloys, and Mg—Y—Gd—Nd alloys. In each alloy, an element may be present in a higher percentage than another element. For example, in an Mg—Y—Gd alloy, magnesium may be present in a higher amount than yttrium and/or gadolinium. However, any relative amount of magnesium, yttrium, and gadolinium may be present. Exemplary embodiments may further include zirconium, zinc, or both. Various embodiments may be more suitable for certain applications, wherein desirable properties have different level of importance.

Non-limiting examples of precipitate phases include Mg24Y5, Mg5Gd, and Mg41Nd5, which are identified according to a standard commercial designation (e.g., ASTM standards developed by ASTM International). For example, the designation Mg24Y5 indicates a ratio of 24 magnesium atoms to 5 yttrium atoms. The precipitate phases may be identified, for example, by ICP-MS measurements down to a precision of about 1-10 ppm depending on the element measured. In general, a particle of precipitate comprises two or more major elements forming the phase, which may identify the phase of the precipitate. However, a precipitate particle may also comprise an additional minor element (e.g., a third element), which may not define the dominant structure of the precipitate particle due to its relatively smaller amount in the phase. In at least some embodiments, the Mg24Y5 precipitate includes some rare earth element other than yttrium, such as gadolinium and/or neodymium. In at least some embodiments, the Mg5Gd precipitate includes some rare earth element other than gadolinium, such as yttrium. In at least some embodiments, the Mg41Nd5 precipitate includes some rare earth element other than neodymium, such as yttrium. In at least one embodiment, the Mg41Nd5 precipitate is formed if there is no gadolinium in the alloy.

In many embodiments, the alloy is formed by a casting and optional heat treatment process. The components of the alloy may be provided to the melt as pure elements, master alloys, or both. The components are melted at a casting temperature to form a liquid, alloy melt. The alloy melt is cooled from the casting temperature. As the alloy is cooled toward room temperature, for example, precipitates may form a portion of the microstructure of the cast alloy. The microstructure may also include one or more phases of precipitates. Desirable properties may be imparted upon the cast alloy because of the identity of the precipitates, the amount of the precipitates, the phase of the precipitates, the location of the precipitates, or any combinations thereof.

The cast alloy may then be heat treated. In some embodiments, the cast alloy is subjected to a range of temperatures in a heat treatment window (e.g., annealing temperatures below the casting temperature). Heat treating may increase the size of precipitate particles and/or refine grain boundaries to impart further desirable properties into the alloy. The precipitate particle sizes may be distributed, for example, as small or large particles. Some precipitate particles may be uniformly or non-uniformly distributed.

In at least some embodiments, one or more master alloys are provided for casting. Non-limiting examples of master alloys include magnesium-gadolinium (Mg—Gd), magnesium-neodymium (Mg—Nd), magnesium-yttrium (Mg—Y), and magnesium-gadolinium-zirconium (Mg—Gd—Zr). Any relative amount of identified element may be may be present in the master alloy (e.g., more, less, or equal relative amounts of magnesium and gadolinium in Mg—Gd). In further embodiments, one or more elements in pure form are provided for casting. In other embodiments, only elements in pure form are provided for casting.

With various aspects of the composition and formation of the alloy being described, various illustrative combinations are also described to further illustrate various combinations of alloy components that may be useful in certain applications, some of which are described herein.

In various illustrative embodiments, an alloy may include, but not be limited to, about:

4-10 wt-% yttrium, 0-9 wt-% heavy REE, 0-7 wt-% light REE, 0-7 wt-% zinc, 0-0.7 wt-% zirconium, and magnesium (optionally comprising the balance of the alloy).

In these particular embodiments, the alloys may exhibit superior strength, ductility, corrosion resistance, or combinations thereof. The alloy may be suitable for a broad range of applications, including mobile and medical applications.

In some illustrative embodiments, alloys may include, but not be limited to, about:

4.5-7.7 wt-% yttrium, 0-9 wt-% heavy REE, 0-6 wt-% light REE, 0-0.3 wt-% zinc, 0-0.5 wt-% zirconium, and magnesium (optionally comprising the balance of the alloy).

In these particular embodiments, the alloys may exhibit superior strength (e.g., due to yttrium-rich precipitates), ductility, corrosion resistance, or combinations thereof. The alloy may be suitable for various medical applications, such as implantable devices.

In further illustrative embodiments, alloys may include, but not be limited to, about:

4.5-7.7 wt-% yttrium (preferably about 5.5-6.7 wt-%), 4-9 wt-% heavy REE (preferably about 5 wt-% or about 5.5-8 wt-%), 0-0.3 wt-% zinc (preferably about 0.2 wt-%), 0-0.5 wt-% zirconium (preferably about 0.4 wt-%), and magnesium (optionally comprising the balance of the alloy).

In these particular embodiments, the alloys may exhibit superior corrosion resistance, ductility, and strength in descending order of importance, which may be a desirable set of properties in medical applications, such as biodegradable stents. Mg24Y5 and/or Mg5Gd may form as precipitate phases in the alloy and may strength the alloy. The precipitates may be very finely distributed having sizes between 5 to 10 microns. Large precipitates may be non-uniformly distributed. Also, corrosion resistance may be comparable to AE42 double melt when compared, for example, by using an ASTM B 117 Salt Fog test.

In additional illustrative embodiments, alloys may include, but not be limited to, about:

4.5-7.7 wt-% yttrium (optionally about 5.5-6.7 wt-%), 0-2 wt-% heavy REE (optionally about 1 wt-%), 4-6 wt-% light REE (optionally about 5 wt-% neodymium), 0-0.3 wt-% zinc (optionally about 0.2 wt-%), 0-0.5 wt-% zirconium (optionally about 0.4 wt-%), and magnesium (optionally comprising the balance of the alloy).

In these particular embodiments, the alloys may exhibit superior ductility, strength, and corrosion resistance in descending order of importance, which may be a desirable set of properties in medical applications, such as bone screws (e.g., spinal), staples, or other fixation devices. Because the corrosion resistance is not as important as in other embodiments, less of the heavy REE may be used when compared to other illustrative embodiments. Also, more light REE than heavy REE may be used. Certain light REEs (e.g., neodymium) may be more readily available than heavy REEs (e.g., gadolinium) and may allow for more cost-effective manufacturing.

In yet further illustrative embodiments, alloys may include, but not be limited to, about:

5.7-10 wt-% yttrium (optionally about 6.7-9 wt-%), 0-3.5 wt-% heavy REE (optionally less than about 2.5 wt-%), 0-0.3 wt-% zinc (optionally about 0.2 wt-%), 0-0.5 wt-% zirconium (optionally about 0.4 wt-%), and magnesium (optionally comprising the balance of the alloy).

In these particular embodiments, the alloys may exhibit superior strength (e.g., due to yttrium-rich precipitates), ductility, and corrosion resistance in descending order of importance. The alloy may be suitable for mobile applications, such as in automobile, bicycle, or aircraft. The higher amount of yttrium than rare earth element may allow for more cost-effective manufacturing and thus may be more suitable in such applications than other embodiments.

In still further illustrative embodiments, alloys may include, but not be limited to, about:

4.5-7.7 wt-% yttrium (optionally about 5.5-6.7 wt-%), 5-7 wt-% light REE (optionally about 6 wt-% neodymium), 0-0.3 wt-% zinc (optionally about 0.2 wt-%), 0-0.5 wt-% zirconium (optionally about 0.4 wt-%), and magnesium (optionally comprising the balance of the alloy).

In these particular embodiments, the alloys may exhibit superior strength (e.g., due to yttrium-rich precipitates), ductility, and corrosion resistance in descending order of importance. The alloy may be suitable for mobile applications, such as in automobile, bicycle, or aicraft. The use of a light REE and yttrium rather than a heavy REE may allow for more cost-effective manufacturing and thus may be more suitable in such applications than other illustrative embodiments.

In some additional illustrative embodiments, alloys may include, but not be limited to, about:

5.7-10 wt-% yttrium (optionally about 6.7-9 wt-%), 0-5.5 wt-% light REE (optionally less than about 4.5 wt-% neodymium), 0-0.3 wt-% zinc (optionally about 0.2 wt-%), 0-0.5 wt-% zirconium (optionally about 0.4 wt-%), and magnesium (optionally comprising the balance of the alloy).

In these particular embodiments, the alloys may exhibit superior strength (e.g., due to yttrium-rich precipitates), ductility, and corrosion resistance in descending order of importance. The alloy may be suitable for mobile applications, such as in automobile, bicycle, or aircraft. The use of a higher amount of yttrium than rare earth element, as well as the use of a light REE rather than a heavy REE, may allow for more cost-effective manufacturing and thus may be more suitable in such applications than other illustrative embodiments.

In various additional illustrative embodiments, alloys may include, but not be limited to, about:

4-6 wt-% yttrium (optionally about 5 wt-%), 4-6 wt-% heavy REE (optionally about 5 wt-%), 0-4 wt-% light REE (optionally no greater than about 3 wt-%), 0-0.3 wt-% zinc (optionally about 0.22 wt-%), 0-0.7 wt-% zirconium (optionally about 0.6 wt-%), and magnesium (optionally comprising the balance of the alloy).

In yet further illustrative embodiments, alloys may include, but not be limited to, about:

4-6 wt-% yttrium (optionally about 5 wt-%), 4-6 wt-% heavy REE (optionally less about 5 wt-%), 0.1-7 wt-% zinc (optionally about 0.22-6 wt-%), 0-0.7 wt-% zirconium (optionally about 0.6 wt-%), and magnesium (optionally comprising the balance of the alloy).

In at least some illustrative embodiments, alloys may include, but not be limited to, about:

4-6 wt-% yttrium (optionally about 5 wt-%), 4-6 wt-% heavy REE (optionally about 5 wt-%), 0-4 wt-% light REE (optionally no greater than about 3 wt-%), 0-0.7 wt-% zirconium (optionally about 0.6 wt-%), and magnesium (optionally comprising the balance of the alloy).

While the present disclosure is not so limited, an appreciation of various aspects of the disclosure will be gained through a discussion of the specific example(s) and illustrative embodiments provided below, which provide alloys with superior mechanical and corrosion properties. Various modifications of the example(s) and illustrative embodiments, as well as additional embodiments of the disclosure, will become apparent herein.

Example 1

Alloys with various illustrative compositions as disclosed herein may have superior mechanical and corrosion performance at least based upon calculations of thermodynamic modeling and/or analysis of casted alloys.

In one example, an example alloy was calculated to cool from a casting temperature in a heat treatment window from about 500 to about 550° C. The example alloy included 5 wt-% yttrium, 5 wt-% gadolinium, 0.4 wt-% zirconium, 0.2 wt-% zinc, and a balance of magnesium (e.g., which can be described as Mg5Gd5Y0.4Zr0.2Zn). A thermodynamic model was calculated to describe the zinc concentration versus temperature for 5Gd5Y without zirconium (e.g., Zr was excluded from the calculations). The model indicated that the above described alloy would have a four phase microstructure including a magnesium phase, an Mg24Y5 phase, an Mg5Gd phase, and an MgGdZn phase.

The example alloy was formed, cast, and analyzed for microstructure properties by CT and SEM. Visualizations of CT data showed an ingot of the example alloy having pores with a volume of about 2 cubic millimeters. Visualizations of SEM data showed precipitates having sizes between 5 to 10 micrometers finely distributed throughout the alloy (see FIG. 1A). The large precipitates were non-uniformly distributed (see FIG. 1B). At least three types of phases were identified (as seen in FIG. 1C), including an MgGd matrix phase 9, a GdMgY phase 10, 11 (e.g., Gd-rich precipitate), MgYGd phase 12, 13, and an MgGd divorced eutectic phase 8. The composition of each phase measured via SEM data is listed in Table I below:

TABLE I Phase % Mg Y Gd MgGd divorced eutectic phase 8 wt-% 86.9 5 8 atm-% 97.09 1.53 1.38 MgGd matrix phase 9 wt-% 96.2 1.6 2.2 atm-% 99.2 0.45 0.35 GdMgY phase 10, 11 wt-% 41.9 5.5 52.5 atm-% 81.31 2.92 15.77 GdMgY phase 12, 13 wt-% 68.5 16.9 14.6 atm-% 90.88 6.13 2.99

The alloy was also analyzed for corrosion performance by ASTM B 117 Salt Fog testing. Samples of the example alloy were provided for testing as small plates having about a 22 millimeter diameter and a 3 millimeter height. The samples were grinded and polished to prepare for salt fog testing at 35° C. for 48 hours. Average corrosion performance was then compared to a control sample of AE42 double melt (AE42 DM), which is one standard commercial designation for Mg-4Al-2RE (indicating about 4 wt-% aluminum, 2 wt-% rare earth element, and a balance of magnesium). The average corrosion depth of the example alloy (about 150 microns) and was found to be comparable to the average corrosion depth of the AE42 DM control sample (about 50 microns).

Example 2

In another example, a heart stent was fabricated with the example alloy described in Example 1. The example heart stent was fabricated by laser cutting. Example heart stent samples were analyzed for corrosion performance soaked in fetal bovine serum. Radial strength testing and quantitative cross-sectional measurements at each end-point of the heart stent were measured at one week, two weeks, and four weeks for samples of the example heart stent and compared against sample stents formed of AE42 magnesium alloy and sample stents formed of WE43 magnesium alloy. The AE42 alloy utilized was described in Example 1. WE43 is one standard commercial designation for another magnesium alloy, which may comprise about 4 wt-% yttrium, about 2.4 to about 4.4 wt-% or rare earth elements, about 0.4 wt-% zirconium, and a balance of magnesium.

According to the radial strength testing, at one week, radial stiffness in the example heart stent samples, as measured in Newtons per millimeter, was observed to be greater than the AE42 samples but less than the WE43 samples. At two weeks, the radial stiffness was observed to be less than both the AE42 and the WE43 samples. At four weeks, the radial stiffness of one example heart stent sample was observed to be greater than both the AE42 and WE43 samples, even though breaks were observed at the crowns at deployment of the example stent samples. Other observations at four weeks included the example heart stent samples having more uniform corrosion than the AE42 samples. The WE43 samples developed corrosion issues at the ends of the stent.

According to the quantitative cross-sectional analysis, the example heart stent showed more fraction metal remaining in the example stent than the WE43 and AE42 samples after one week. After two weeks, the fractional metal remaining was about the same as the AE42 samples and more than the WE43 samples. The arms of the example stent samples and the WE43 samples fell apart after four weeks. Only the AE42 samples were measured at four weeks and showed a significant drop in fraction metal remaining compared to the two week measurement.

Illustrative Embodiments

Embodiment 1 is an alloy comprising a rare earth element alloy component in an amount greater than about 6 wt-%, comprising yttrium in an amount greater than about 2 wt-% and a rare earth element other than yttrium in an amount greater than about 1 wt-%, and magnesium in an amount up to about 90 wt-%. The rare earth element other than yttrium may be selected from gadolinium, dysprosium, erbium, neodymium, lanthanum, cerium, and combinations thereof (e.g., heavy or light rare earth elements).

Embodiment 2 is an alloy comprising a rare earth element alloy component, comprising yttrium in an amount greater than about 3 wt-% and a rare earth element other than yttrium in an amount greater than about 1%, and magnesium in an amount up to about 90 wt-%. The rare earth element other than yttrium may be selected from gadolinium, dysprosium, erbium, neodymium, lanthanum, cerium, and combinations thereof (e.g., heavy or light rare earth elements).

Embodiment 3 is an alloy comprising a rare earth element alloy component, comprising yttrium in an amount greater than about 3 wt-% and a heavy rare earth element other than yttrium in an amount no less than about 0.1 wt-%, and magnesium in an amount up to about 90 wt-%. The heavy rare earth element may be selected from gadolinium, dysprosium, erbium, and combinations thereof (e.g., heavy rare earth elements).

Embodiment 4 is an alloy comprising a rare earth element alloy component in an amount no less than about 10 wt-%, comprising yttrium in an amount greater than about 2 wt-% and a rare earth element other than yttrium in an amount greater than about 1 wt-%, and magnesium in an amount up to a balance of the alloy. The rare earth element other than yttrium may be selected from gadolinium, dysprosium, erbium, neodymium, lanthanum, cerium, and combinations thereof (e.g., heavy or light rare earth elements).

Embodiment 5 is the alloy of any one of embodiments 1 through 4 comprising a precipitate impurity phase of Mg24Y5 and optionally a rare earth element.

Embodiment 6 is the alloy of any one of embodiments 1 through 5 comprising a precipitate impurity phase of Mg5Gd and optionally yttrium, as applicable.

Embodiment 7 is the alloy of any one of embodiments 1 through 5 comprising a precipitate impurity phase of Mg41Nd5 and optionally yttrium, as applicable.

Embodiment 8 is the alloy of any one of embodiments 1 through 7 comprising zinc in an amount no less than about 0.1 wt-% and/or no greater than about 7 wt-%.

Embodiment 9 is the alloy of embodiment 8, wherein the amount of zinc is no greater than about 0.3 wt-%.

Embodiment 10 is the alloy of embodiment 9, wherein the amount of zinc is about 0.2 wt-%.

Embodiment 11 is the alloy of embodiment 8, wherein the amount of zinc is no less than about 0.2 wt-%.

Embodiment 12 is the alloy of embodiment 8, wherein the amount of zinc is no greater than about 7 wt-%.

Embodiment 13 is the alloy of any one of embodiments 11, and 12, wherein the amount of zinc is no less than about 0.22 wt-% and/or no greater than about 6 wt-%.

Embodiment 14 is the alloy of embodiment 13, wherein the amount of zinc is about 0.22 wt-%.

Embodiment 15 is the alloy of embodiment 8, wherein the amount of zinc is greater than about 0.5 wt-%.

Embodiment 16 is the alloy of any one of embodiments 1 through 7, comprising a substantial absence of zinc (e.g., less than about 1 wt-%, 0.1 wt-%, 0.05 wt-%, etc).

Embodiment 17 is the alloy of any one of embodiments 1 through 16, comprising zirconium in an amount no less than about 0.3 wt-% and/or no greater than about 0.7 wt-%.

Embodiment 18 is the alloy of embodiment 17, wherein the amount of zirconium is no greater than about 0.5 wt-%.

Embodiment 19 is the alloy of embodiment 18, wherein the amount of zirconium is about 0.4 wt-%.

Embodiment 20 is the alloy of embodiment 17, wherein the amount of zirconium is no less than about 0.5 wt-%.

Embodiment 21 is the alloy of embodiment 20, wherein the amount of zirconium is about 0.6 wt-%.

Embodiment 22 is the alloy of any one of embodiments 1 through 15 comprising a substantial absence of zirconium (e.g., less than about 1 wt-%, 0.1 wt-%, 0.05 wt-%, etc).

Embodiment 23 is the alloy of any one of embodiments 1 through 22, wherein the magnesium is in an amount up to about 90 wt-%, as applicable.

Embodiment 24 is the alloy of embodiment 23, wherein the magnesium is in an amount up to about 89.5 wt-%.

Embodiment 25 is the alloy of any one of embodiments 1 through 24, wherein the amount of yttrium is no less than about 4 wt-% and/or no greater than about 10 wt-%.

Embodiment 26 is the alloy of embodiment 25, wherein the amount of yttrium is greater than about 4.5 wt-%.

Embodiment 27 is the alloy of embodiment 25, wherein the amount of yttrium is less than about 7.7 wt-%.

Embodiment 28 is the alloy of any one of embodiments 26 and 27, wherein the amount of yttrium is no less than about 5 wt-% and/or no greater than about 7 wt-%.

Embodiment 29 is the alloy of embodiment 28, wherein the amount of yttrium is no less than about 5.5 wt-% and/or no greater than about 6.7 wt-%.

Embodiment 30 is the alloy of embodiment 25, wherein the amount of yttrium is no less than about 4 wt-%, as applicable.

Embodiment 31 is the alloy of embodiment 25, wherein the amount of yttrium of yttrium no greater than about 6 wt-%.

Embodiment 32 is the alloy of any one of embodiments 30 and 31, wherein the amount of yttrium is about 5 wt-%.

Embodiment 33 is the alloy of embodiment 25, wherein the amount of yttrium is no less than about 5.7 wt-%.

Embodiment 34 is the alloy of embodiment 25, wherein the amount of yttrium is no greater than about 10 wt-%, as applicable.

Embodiment 35 is the alloy of any one of embodiments 33 and 34, wherein the amount of yttrium is no less than about 6 wt-% and/or no greater than about 10 wt-%, as applicable.

Embodiment 36 is the alloy of embodiment 35, wherein the amount of yttrium is no less than about 6.7 wt-% and/or no greater than about 9 wt-%.

Embodiment 37 is the alloy of any one of embodiments 1 through 36, wherein the amount of yttrium is greater than 3 wt-%, as applicable.

Embodiment 38 is the alloy of any one of embodiments 1 through 36, wherein the amount of yttrium is greater than about 5.5 wt-%, as applicable.

Embodiment 39 is the alloy of any one of embodiments 1 through 38, wherein the rare earth element other than yttrium is selected from a heavy rare earth element, a light rare earth element, and combinations thereof, as applicable.

Embodiment 40 is the alloy of embodiment 39, wherein the rare earth element other than yttrium is gadolinium, dysprosium, erbium, and combinations thereof (e.g., heavy rare earth elements).

Embodiment 41 is the alloy of embodiment 40, wherein the rare earth element other than yttrium is gadolinium.

Embodiment 42 is the alloy of embodiment 39, wherein the rare earth element other than yttrium is selected from neodymium, lanthanum, cerium, and combinations thereof (e.g., light rare earth elements).

Embodiment 43 is the alloy of embodiment 42, wherein the rare earth element other than yttrium is neodymium.

Embodiment 44 is the alloy of embodiment 39, wherein the rare earth element other than yttrium comprises a heavy rare earth element and a light rare earth element.

Embodiment 45 is the alloy of embodiment 44, wherein the light rare earth element comprises neodymium.

Embodiment 46 is the alloy of any one of embodiments 44 and 45, wherein the heavy rare earth element comprises gadolinium.

Embodiment 47 is the alloy of embodiment 39, wherein the amount of the yttrium is greater than or equal to the amount of rare earth element other than yttrium (e.g., REE less than or equal to yttrium).

Embodiment 48 is the alloy of embodiment 39, wherein the amount of yttrium is less than or equal to the amount of rare earth element other than yttrium (e.g., REE is greater than or equal to yttrium).

Embodiment 49 is the alloy of embodiment 39, wherein the amount of yttrium is about equal to the rare earth element other than yttrium (e.g., within about 5%, within about 10%, within about 20%, within about 25%, within about 33%, etc).

Embodiment 50 is the alloy of any one of embodiments 44 through 46, wherein the amount of the heavy rare earth element is greater than the amount of light rare earth element.

Embodiment 51 is the alloy of any one of embodiments 44 through 46, wherein the amount of the heavy rare earth element is less than the amount of light rare earth element.

Embodiment 52 is the alloy of any one of embodiments 50 and 51, wherein the amount of the heavy rare earth element is about equal to the amount of yttrium.

Embodiment 53 is the alloy of embodiment 39, wherein the amount of the rare earth element other than yttrium is no less than about 0.1 wt-% and/or no greater than about 9 wt-%

Embodiment 54 is the alloy of embodiment 39, wherein the amount of the rare earth element other than yttrium is no less than about 4 wt-%.

Embodiment 55 is the alloy of embodiment 39, wherein the amount of the rare earth element other than yttrium is no greater than about 6 wt-%.

Embodiment 56 is the alloy of any one of embodiments 54 and 55, wherein the amount of the rare earth element other than yttrium is about 5 wt-%.

Embodiment 57 is the alloy of embodiment 39, wherein the amount of the rare earth element other than yttrium is no less than about 4.5 wt-%.

Embodiment 58 is the alloy of embodiment 39, wherein the amount of the rare earth element other than yttrium is no greater than about 9 wt-%, as applicable.

Embodiment 59 is the alloy of any one of embodiments 57 and 58, wherein the amount of the rare earth element other than yttrium is no less than about 5 wt-%.

Embodiment 60 is the alloy of embodiment 59, wherein the amount of the rare earth element other than yttrium is no less than about 5.5 wt-% and/or no greater than about 8 wt-%.

Embodiment 61 is the alloy of embodiment 39, wherein the amount of the rare earth element other than yttrium is no greater than about 2 wt-%.

Embodiment 62 is the alloy of embodiments 61, wherein the amount of the rare earth element other than yttrium is about 1 wt-%.

Embodiment 63 is the alloy of embodiment 39, wherein the amount of the rare earth element other than yttrium is no greater than about 3.5 wt-%.

Embodiment 64 is the alloy of embodiment 63, wherein the amount of the rare earth element other than yttrium is no greater than about 3 wt-%.

Embodiment 65 is the alloy of embodiment 64, wherein the amount of the rare earth element other than yttrium is less than about 2.5 wt-%.

Embodiment 66 is the alloy of embodiment 39, wherein the amount of the rare earth element other than yttrium is no less than about 5 wt-%.

Embodiment 67 is the alloy of embodiment 39, wherein the amount of the rare earth element other than yttrium is no greater than about 7 wt-%.

Embodiment 68 is the alloy of any one of embodiments 66 and 67, wherein the amount of the rare earth element other than yttrium is about 6 wt-%.

Embodiment 69 is the alloy of embodiment 39, wherein the amount of the rare earth element other than yttrium is less than about 5.5 wt-%.

Embodiment 70 is the alloy of embodiment 69, wherein the amount of the rare earth element other than yttrium is less than about 5 wt-%.

Embodiment 71 is the alloy of embodiment 70, wherein the amount of the rare earth element other than yttrium is less than about 4.5 wt-%.

Embodiment 72 is the alloy of embodiment 39, wherein the amount of the rare earth element other than yttrium is less than about 4 wt-%.

Embodiment 73 is the alloy of embodiment 72, wherein the amount of the rare earth element other than yttrium is less than about 3 wt-%.

Embodiment 74 is the alloy of any one of embodiments 1 through 73, wherein the amount of the rare earth element other than yttrium is greater than about 3 wt-%, as applicable.

Embodiment 75 is the alloy of any one of embodiments 1 through 73, wherein the amount of the rare earth element other than yttrium is greater than about 5.5 wt-%, as applicable.

Embodiment 76 is the alloy of any one of embodiments 53 through 62, wherein the rare earth element is a heavy rare earth element.

Embodiment 77 is the alloy of embodiment 76, wherein the heavy rare earth element is gadolinium.

Embodiment 78 is the alloy of any one of embodiments 53 through 56 and 66 through 73, wherein the rare earth element is a light rare earth element.

Embodiment 79 is the alloy of embodiment 78, wherein the light rare earth element is neodymium.

Embodiment 80 is the alloy of any one of embodiments 53 through 79, wherein the rare earth element other than yttrium comprises only one rare earth element.

Embodiment 81 is the alloy of any one of embodiments 53 and 54, wherein the rare earth element is no less than about 5 wt-% and/or no greater than about 8 wt-%.

Embodiment 82 is the alloy of any one of embodiments 81 and 66 through 68, wherein the rare earth element other than yttrium comprises two or more rare earth elements other than yttrium.

Embodiment 83 is the alloy of embodiment 82, wherein the two or more rare earth elements other than yttrium comprise a heavy rare earth element and a light rare earth element.

Embodiment 84 is the alloy of embodiment 83, wherein the light rare earth element comprises neodymium.

Embodiment 85 is the alloy of any one of embodiments 83 and 84, wherein the heavy rare earth element comprises gadolinium.

Embodiment 86 is the alloy of any one of embodiments 1 through 85, wherein the amount of the rare earth element alloy component is greater than about 5 wt-% and less than about 16 wt-%, as applicable.

Embodiment 87 is the alloy of embodiment 86, wherein the amount of the rare earth element alloy component is no less than about 9 wt-%, as applicable.

Embodiment 88 is the alloy of embodiment 86, wherein the amount of the rare earth element alloy component is no greater than about 13 wt-%, as applicable.

Embodiment 89 is the alloy of any one of embodiments 87 or 88, wherein the amount of the rare earth element alloy component is no less than about 9.5 wt-% and/or no greater than about 12.7 wt-%.

Embodiment 90 is the alloy of embodiment 89 wherein the amount of the rare earth element alloy component is no less than about 10.5 wt-% and/or no greater than about 11.7 wt-%.

Embodiment 91 is the alloy of embodiment 86, wherein the amount of the rare earth element alloy component is no less than about 10 wt-%, as applicable.

Embodiment 92 is the alloy of embodiment 86, wherein the amount of the rare earth element alloy component is no greater than about 16 wt-%, as applicable.

Embodiment 93 is the alloy of any one of embodiments 91 and 92, wherein the amount of the rare earth element alloy component is no less than about 10 wt-% and/or no greater than about 15.7 wt-%.

Embodiment 94 is the alloy of embodiment 93, wherein the amount of the rare earth element alloy component is no less than about 11 wt-% and/or no greater than about 14.7 wt-%.

Embodiment 95 is the alloy of any one of embodiments 88 and 90, wherein the amount of the rare earth element alloy component is no less than about 10.5 wt-% and/or no greater than about 13.7 wt-%.

Embodiment 96 is the alloy of embodiment 95, wherein the amount of the rare earth element alloy component is no less than about 11.5 wt-% and/or no greater than about 12.7 wt-%.

Embodiment 97 is the alloy of embodiment 86, wherein the amount of the rare earth element alloy component is no greater than about 14 wt-%, as applicable.

Embodiment 98 is the alloy of any one of embodiments 87 and 97, wherein the amount of the rare earth element alloy component is no less than about 9 wt-% and/or no greater than about 14 wt-%.

Embodiment 99 is the alloy of embodiment 98, wherein the amount of the rare earth element alloy component is no less than about 10 wt-% and/or no greater than about 13 wt-%.

Embodiment 100 is the alloy of embodiment 86, wherein the amount of the rare earth element alloy component is no greater than about 13 wt-%, as applicable.

Embodiment 101 is the alloy of any one of embodiments 86 and 100, wherein the amount of the rare earth element alloy component is no less than about 5.7 wt-% and/or no greater than about 12.5 wt-%.

Embodiment 102 is the alloy of embodiment 101, wherein the amount of the rare earth element alloy component is no less than about 6.7 wt-% and/or no greater than about 11.5 wt-%.

Embodiment 103 is the alloy of embodiment 86, wherein the amount of the rare earth element alloy component is no greater than about 15 wt-%, as applicable.

Embodiment 104 is the alloy of any one of embodiments 86 and 103, wherein the amount of the rare earth element alloy component is no less than about 5.7 wt-% and/or no greater than about 14.5 wt-%.

Embodiment 105 is the alloy of embodiment 104, wherein the amount of the rare earth element alloy component is no less than about 6.7 wt-% and/or no greater than about 13.5 wt-%.

Embodiment 106 is the alloy of embodiment 86, wherein the amount of the rare earth element alloy component is no greater than about 11 wt-%, as applicable.

Embodiment 107 is the alloy of any one of embodiments 87 and 106, wherein the amount of the rare earth element alloy component is about 10 wt-%.

Embodiment 108 is the alloy of embodiment 86, wherein the amount of the rare earth element alloy component is greater than about 6 wt-%.

Embodiment 109 is the alloy of any one of embodiments 86 through 94, 100 through 102, 106, and 107, wherein the rare earth element is a heavy rare earth element.

Embodiment 110 is the alloy of any one of embodiments 86 through 90, 95, 96, and 103 through 105, wherein the rare earth element is a light rare earth element.

Embodiment 111 is the alloy of any one of embodiments 86 through 90 and 94 through 99, wherein the rare earth element comprises a heavy rare earth element and a light rare earth element.

Embodiment 112 is the alloy of any one of embodiments 1 through 111 wherein the amount of at least one of the yttrium and the rare earth element is greater than the amount corresponding to one-half the respective solid solubility in magnesium, as applicable.

Embodiment 113 is the alloy of any one of embodiments 1 through 112 comprising a substantial absence of scandium (e.g., less than about 1 wt-%, 0.1 wt-%, 0.05 wt-%, etc).

Embodiment 114 is the alloy of any one of embodiments 1 through 113 comprising a substantial absence of calcium (e.g., less than about 1 wt-%, 0.1 wt-%, 0.05 wt-%, etc).

Embodiment 115 is the alloy of any one of embodiments 1 through 114 comprising a substantial absence of indium (e.g., less than about 1 wt-%, 0.1 wt-%, 0.05 wt-%, etc).

Embodiment 116 is the alloy of any one of embodiments 1 through 115 wherein the alloy comprises a balance of magnesium.

Thus, embodiments of the MAGNESIUM AND RARE EARTH ELEMENT ALLOY are disclosed. All references and publications cited herein are expressly incorporated herein by reference in their entirety into this disclosure, except to the extent they may directly contradict this disclosure. Although specific embodiments have been described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations can be substituted for the specific embodiments described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof. The disclosed embodiments are presented for purposes of illustration and not limitation. 

What is claimed is:
 1. An alloy comprising: a rare earth element alloy component in an amount greater than 6 wt-% comprising: yttrium in an amount greater than 2 wt-%; and a rare earth element other than yttrium in an amount greater than 1% selected from gadolinium, dysprosium, erbium, neodymium, lanthanum, cerium, and combinations thereof; and magnesium in an amount up to 90 wt-%.
 2. The alloy according to claim 1, wherein the amount of yttrium is no less than 4.5 wt-%.
 3. The alloy according to claim 2, wherein the amount of the rare earth element other than yttrium is no less than 4 wt-%.
 4. The alloy according to claim 3, wherein the amount of the rare earth element alloy component is no less than 9.5 wt-%.
 5. The alloy according to claim 3, wherein the rare earth element other than yttrium is a heavy rare earth element selected from gadolinium, dysprosium, and erbium.
 6. The alloy according to claim 2, wherein the amount of the rare earth element other than yttrium is no less than 5 wt-%.
 7. The alloy according to claim 6, wherein the rare earth element other than yttrium comprises a combination of two rare earth elements other than yttrium.
 8. The alloy according to claim 7, wherein the rare earth element other than yttrium comprises a heavy rare earth element and a light rare earth element, wherein the heavy rare earth element is selected from gadolinium, dysprosium, erbium, and combinations thereof, wherein the light rare earth element is selected from neodymium, lanthanum, and cerium, and combinations thereof.
 9. The alloy according to claim 8, wherein the amount of the heavy rare earth element is greater than the amount of the light rare earth element.
 10. The alloy according to claim 1, wherein the amount of yttrium is greater than or equal to the amount of the rare earth element other than yttrium.
 11. The alloy according to claim 1, further comprising at least one of zinc in an amount greater than 0.1 wt-% and zirconium in an amount greater than 0.3 wt-%.
 12. The alloy according to claim 1, comprising a substantial absence of an element selected from: scandium in an amount less than 1 wt-%, calcium in an amount less than 0.05 wt-%, indium in an amount less than 0.1 wt-%, and combinations thereof.
 13. An alloy comprising: a rare earth element alloy component comprising: yttrium in an amount greater than 3 wt-%; and a rare earth element other than yttrium in an amount greater than 1% selected from gadolinium, dysprosium, erbium, neodymium, lanthanum, cerium, and combinations thereof; and magnesium in an amount up to 90 wt-%.
 14. The alloy according to claim 13, wherein an amount of the rare earth element alloy component is no less than 9.5 wt-%.
 15. The alloy according to claim 14, wherein the rare earth element other than yttrium comprises a combination of two rare earth elements other than yttrium.
 16. An alloy comprising: a rare earth element alloy component comprising: yttrium in an amount greater than 3 wt-%; and a heavy rare earth element other than yttrium in an amount no less than 0.1 wt-% selected from gadolinium, dysprosium, erbium, and combinations thereof; and magnesium in an amount up to 90 wt-%.
 17. The alloy according to claim 16, wherein an amount of the rare earth element alloy component is no less than 9.5 wt-%.
 18. An alloy comprising: a rare earth element alloy component in an amount no less than 10 wt-% comprising: yttrium in an amount greater than 2 wt-%; and a rare earth element other than yttrium in an amount greater than 1 wt-% selected from gadolinium, dysprosium, erbium, neodymium, lanthanum, cerium, and combinations thereof; and magnesium in an amount up to a balance of the alloy.
 19. The alloy according to claim 18, wherein an amount of the rare earth element alloy component is no less than 9.5 wt-%.
 20. The alloy according to claim 18, comprising a substantial absence of an element selected from: scandium in an amount less than 1 wt-%, calcium in an amount less than 0.05 wt-%, indium in an amount less than 0.1 wt-%, and combinations thereof. 